Direct Observation of Unusual Interfacial Dzyaloshinskii-Moriya Interaction in Graphene/NiFe/Ta Heterostructure

TL;DR

This study directly observes interfacial Dzyaloshinskii-Moriya interaction (iDMI) in a graphene/NiFe/Ta heterostructure, revealing its dependence on interface defects and thickness, with implications for spintronic device design.

Contribution

It provides the first direct measurement of iDMI at a graphene/ferromagnet interface and links its origin to defect-induced extrinsic spin-orbit coupling.

Findings

iDMI scales inversely with NiFe thickness

iDMI and spin-mixing conductance increase with graphene defect density

iDMI observed without perpendicular magnetic anisotropy

Abstract

Graphene/ferromagnet interface promises a plethora of new science and technology. The interfacial Dzyaloshinskii Moriya interaction (iDMI) is essential for stabilizing chiral spin textures, which are important for future spintronic devices. Here, we report direct observation of iDMI in graphene/Ni80Fe20/Ta heterostructure from non-reciprocity in spin-wave dispersion using Brillouin light scattering (BLS) technique. Linear scaling of iDMI with the inverse of Ni80Fe20 thicknesses suggests primarily interfacial origin of iDMI. Both iDMI and spin-mixing conductance increase with the increase in defect density of graphene obtained by varying argon pressure during sputter deposition of Ni80Fe20. This suggests that the observed iDMI originates from defect-induced extrinsic spin-orbit coupling at the interface. The direct observation of iDMI at graphene/ferromagnet interface without perpendicular magnetic anisotropy opens new route in designing thin film heterostructures based on 2-D materials for controlling chiral spin structure such as skyrmions and bubbles, and magnetic domain-wall-based storage and memory devices.